Killer Max Version 2 Part I

For the first part of the alteration, I wish to change the chassis of the robot.

Prof Mason have suggest me that my tank tread can change so my tank can have more traction.
So I plan to change the design of the wheels. Instead having the ability to climb up opponent's robot, it will have more traction with the ground.
Also, one of my weakness with the vers 1 is the weight of the robot is too light and the additional weight is position on the top which will affect the center of the mass and leads to tilt over and fall to the side.
As for right now, the chassis will be alter so the front wheels and the back wheels can be horizontal. Also, I wish to add additional twin engine gear box to the front two wheels, so the tank will be four wheel drive.
The new gear box has been already assemble to the same gear ratio as the old one. However, they will have different motor engine, which I wish to test it out to see if it will affect the overall performance.

My biggest problem now is to fit both gear box on my chassis and still within the restricted size of the robot.